Just like farm animals, wolves will now no longer despawn, and they now spawn rarely. Most wolves will now generate with the world. Wolves will now despawn only when hostile; passive and tamed wolves do not.

Can Tame wolf Despawn Minecraft?

They do not despawn, even if they are in an unloaded chunk, or 32 blocks away from the player.

Will my wolf Despawn?

Night-spawned wolves of any level will only eat, breed, and follow at night time, even after you've tamed them. They may even despawn completely during the day, at which point you'll lose them as tamed companions.